Photoluminescence of zircon (ZrSiO4) doped with REE3+ (REE = Pr, Sm, Eu, Gd, Dy, Ho, Er)

The photoluminescence properties of synthetic zircon, ZrSiO₄, doped with REE³⁺ (REE = Pr, Sm, Eu, Gd, Dy, Ho, Er) were investigated using combined excitation and emission spectroscopy. All samples showed luminescence characteristics of intra-ion energy transitions, similar to other lanthanide-doped materials. However, the relative intensities were dependent on the energy of excitation and the presence of charge-transfer bands were inferred from excitation spectra. From the data, we conclude that the lanthanides in zircon occur in more than one type of coordination. Energy transfer between different lanthanides was observed in some co-doped samples and emissions that were unassigned in previous studies have been assigned to specific lanthanides based on excitation spectroscopy.     

Leaky savannas: the significance of lateral carbon fluxes in the seasonal tropics

Globally, dissolved inorganic carbon (DIC) accounts for more than half the annual flux of carbon exported from terrestrial ecosystems via rivers. Here, we assess the relative influences of biogeochemical and hydrological processes on DIC fluxes exported from a tropical river catchment characterized by distinct land cover, climate and geology transition from the wet tropical mountains to the low‐lying savanna plains. Processes controlling changes in river DIC were investigated using dissolved organic carbon, particulate organic carbon and DIC concentrations and stable isotope ratios of DIC (δ¹³C_DIC) at two time scales: seasonal and diel. The recently developed Isotopic Continuous Dissolved Inorganic Carbon Analyser was used to measure diel DIC concentration and δ¹³C_DIC changes at a 15‐min temporal resolution. Results highlight the predominance of biologically mediated processes (photosynthesis and respiration) controlling diel changes in DIC. These resulted in DIC concentrations varying between 3.55 and 3.82 mg/l and δ¹³C_DIC values ranging from ?19.7 ± 0.31‰ to ?17.1 ± 0.08‰. In contrast, at the seasonal scale, we observed wet season DIC variations predominantly from mixing processes and dry season DIC variations due to both mixing processes and biological processes. The observed wet season increases in DIC concentrations (by 6.81 mg/l) and δ¹³C_DIC values of river water (by 5.4‰) largely result from proportional increases in subsurface inflows from the savanna plains (C₄ vegetation) region relative to inflows from the rainforest (C₃ vegetation) highlands. The high DIC river load during the wet season resulted in the transfer of 97% of the annual river carbon load. Therefore, in this gaining river, there are significant seasonal variations in both the hydrological and carbon cycles, and there is evidence of substantial coupling between the carbon cycles of the terrestrial and the fluvial environments. Recent identification of a substantial carbon sink in the savannas of northern Australia during wetter years in the recent past does not take into account the possibility of a substantial, rapid, lateral flux of carbon to rivers and back to the atmosphere. Copyright © 2015 John Wiley & Sons, Ltd.     

Extinction chronology of the cave lion Panthera spelaea

The cave lion, Panthera spelaea, was widespread across northern Eurasia and Alaska/Yukon during the Late Pleistocene. Both morphology and DNA indicate an animal distinct from modern lions (probably at the species level) so that its disappearance in the Late Pleistocene should be treated as a true extinction. New AMS radiocarbon dates directly on cave lion from across its range, together with published dates from other studies – totalling 111 dates – indicate extinction across Eurasia in the interval ca. 14–14.5 cal ka BP, and in Alaska/Yukon about a thousand years later. It is likely that its extinction occurred directly or indirectly in response to the climatic warming that occurred ca. 14.7 cal ka BP at the onset of Greenland Interstadial 1, accompanied by a spread of shrubs and trees and reduction in open habitats. Possibly there was also a concomitant reduction in abundance of available prey, although most of its probable prey species survived substantially later. At present it is unclear whether human expansion in the Lateglacial might have played a role in cave lion extinction. Gaps in the temporal pattern of dates suggest earlier temporary contractions of range, ca. 40–35 cal ka BP in Siberia (during MIS 3) and ca. 25–20 cal ka BP in Europe (during the ‘Last Glacial Maximum’), but further dates are required to corroborate these. The Holocene expansion of modern lion (Panthera leo) into south-west Asia and south-east Europe re-occupied part of the former range of P. spelaea, but the Late Pleistocene temporal and geographical relationships of the two species are unknown.     

MegaZ-LRG: a photometric redshift catalogue of one million SDSS luminous red galaxies

We describe the construction of MegaZ-LRG, a photometric redshift catalogue of over one million luminous red galaxies (LRGs) in the redshift range  0.4 < z < 0.7  with limiting magnitude   i < 20  . The catalogue is selected from the imaging data of the Sloan Digital Sky Survey (SDSS) Data Release 4. The 2dF-SDSS LRG and Quasar (2SLAQ) spectroscopic redshift catalogue of 13 000 intermediate-redshift LRGs provides a photometric redshift training set, allowing use of ann z, a neural network-based photometric-redshift estimator. The rms photometric redshift accuracy obtained for an evaluation set selected from the 2SLAQ sample is  σ _z = 0.049  averaged over all galaxies, and  σ _z = 0.040  for a brighter subsample  ( i < 19.0)  . The catalogue is expected to contain ∼5 per cent stellar contamination. The ann z code is used to compute a refined star/galaxy probability based on a range of photometric parameters; this allows the contamination fraction to be reduced to 2 per cent with negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly available on the World Wide Web from http://www.2slaq.info .     

Internal structure of a trough blowout, determined from migrated ground-penetrating radar profiles

Ground‐penetrating radar (GPR) was used to investigate the relationship between the geomorphological development of a large aeolian trough blowout and the stratigraphy and internal sedimentary structure of its associated deposits. Although analogous, many of the data‐processing techniques routinely applied in seismic reflection are very rarely applied in GPR studies. In this study, a simple migration program was used that significantly enhanced the quality of GPR images from a large trough blowout at Raven Meols on the Sefton coast, northwest England. These improvements aided subsequent data interpretation, which was achieved through application of the principles of radar stratigraphy. GPR shows the pre‐blowout dunes to have a complex internal structure that suggests they were formed in the presence of at least a partial vegetation cover. Subsequent to stabilization of these dunes a thin soil developed. This dune soil forms an important radar sequence boundary and delineates a complex topography beneath the depositional lobe of the blowout. The internal structure of the depositional lobe of the blowout does not conform to a model of simple radial foreset deposition, as derived from contemporary process studies reported in the literature. Instead, the pattern of deposition has been extensively modified by the antecedent dune topography and by varying spatial and temporal exposure to important sand‐transporting winds that is partly controlled by interactions between the regional wind pattern and local dune morphology. Trough blowout deposits in coastal aeolian sedimentary sequences are likely to be recognized by the presence of laterally continuous packets of relatively high‐angle cross‐strata, which often display a spatially‐variable radial dip pattern that is only very poorly or partially developed. In addition, a soil, or other surface representing a significant hiatus in dune deposition, is likely to underlie the blowout deposits, the topography of which will show a clear relationship to the dip and orientation of the overlying cross‐strata.     

Lobster is big in Boston: Postcards,place commodification,and tourism

An analysis of picture postcards from Boston, Massachusetts shows that, in 1977, Boston was portrayed as a center of heritage and science and technology. In 1990 more postcards featured more views of more sights, emphasising shopping and academe. A new class of novelty cards conveyed images of Boston which did not refer to any particular geographic sites. We interpret these shifts using the idea of place commodification and by situating tourism in the culture industry.     

Correlation between joint orientation and geophysical stresses in a test area on the Canadian Shield

SummaryCorrelation Between Joint Orientation and Geophysical Stresses in a Test Area on the Canadian Shield It is contended that the orientation of the geophysical stress field in an area can be deduced from an analysis of the orientation of the joints which it has produced. As a test area, a reasonably homogeneous region of the Canadian Shield in the vicinity of Three-Mile-Lake in Ontario (roughly lat. 45° 10N and longitude 79° 25W) was chosen for analysis. It was found that the stresses were indeed homogeneous over an area of about 10 × 4 km with the exception of a small area which also shows petrographic and geomorphic peculiarities. Thus, local tectonic anomalies can immediately be recognized in the joint patterns.

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ZusammenfassungKorrelation zwischen der Lage von Klüften und dem geophysikalischen Spannungsfeld in einem Testgebiet im kanadischen Schild Es wird die Hypothese aufgestellt, daß die Hauptachsenrichtungen des geophysikalischen Spannungsfeldes aus der Lage der von ihm verursachten Klüfte abgeleitet werden kann. Um die Hypothese zu prüfen, wurde ein verhältnismäßig homogenes Gebiet des kanadischen Schildes in der Nähe vom Three-Mile-See in Ontario (ungefähr 45° 10N Breite und 79° 25W Länge) ausgewählt. Es wurde festgestellt, daß das abgeleitete Spannungsfeld über ein Gebiet von 40 km² tatsächlich homogen ist, mit Ausnahme einer kleinen Fläche, welche auch petrographische und geomorphologische Anomalien aufweist. Es können daher tektonische Anomalien sofort in den Klüftediagrammen erkannt werden.

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RésuméCorrelation entre l'orientation des clivages et les contraintes tectoniques dans une région d'épreuve du bouclier Canadien L'hypothèse est maintenue que l'orientation du champ des contraintes tectoniques peut être déduite par une analyse de l'orientation des clivages qu'il a produite. Comme région d'épreuve, une région à peu près homogène du bouclier Canadien dans le voisinage du Lac-des-Trois-Miles (45° 10N, 79° 25W) a été choisie. Il est démontré que les contraintes sont actuellement homogènes dans une région de 40 km², y exceptée une petite région où l'on observe aussi des péculiarités pétrographiques et géomorphologiques. Ainsi, les anomalies tectoniques locales peuvent être reconnues immédiatement dans les dessins du clivage.

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With 14 Figures